1. Field of the Invention
The present invention relates to a flux supply device, and particularly to a flux supply device and a liquid flux supply method for supplying a mixed gas to a brazing apparatus.
2. Description of the Background Art
FIG. 8 is a diagram schematically showing the structure of a conventional brazing apparatus.
Referring to FIG. 8, the flux storage tank 11, shaped like a bottle having an observation hatch 13, contains about 1.5 liters of liquid flux 15. A gas blow-in pipe 18 is attached to the lid 14 of the flux storage tank 11, with the lower end of the gas blow-in pipe 18 located below the surface level S1 of the liquid flux 15. The gas blow-in pipe 18 is connected through a gas pipe 19 and a manual valve 70 to a combustible gas cylinder 67 charged with a combustible gas such as propane, acetylene, etc.
In the use of the gas flux, the liquid flux 15 in the flux storage tank 11 diminishes. Therefore a liquid flux replenishing device is provided to replenish the liquid flux. This liquid flux replenishing device includes a replenishing tank 25 as its major component. That is to say, the liquid flux replenishing device is composed of: the replenishing tank 25 containing the liquid flux 15; a first pipe 41 connected to the opening 26 of the replenishing tank 25; a first manual valve 31 connected to the lower end of the first pipe 41; a second pipe 42 connected to the lower end of the first manual valve 31; a cam lock coupling 32 allowing the second pipe 42 to be attached and removed; a third pipe 65 connected to the lower end of the cam lock coupling 32; a second manual valve 35 connected to the lower end of the third pipe 65; and a liquid flux supply pipe 17 connected to the lower end of the second manual valve 35 and disposed to protrude in the flux storage tank 11 through the lid 14.
When the first and second manual valves 31 and 35 are both opened, the liquid flux 15 contained in the replenishing tank 25 is supplied into the flux storage tank 11 through the first pipe 41, second pipe 42, third pipe 65, and liquid flux supply pipe 17. The surface level S1 of the liquid flux 15 in the flux storage tank 11 is thus defined by the position of the lower end of the liquid flux supply pipe 17.
An outlet 21 is attached to the lid 14 of the flux storage tank 11 to send out the mixed gas produced in the flux storage tank 11, and a mixed gas pipe 20 is connected to the outlet 21 and to an automatic brazing apparatus 76 via a manual valve 72.
The automatic brazing apparatus 76 is connected to a burning-supporting gas cylinder 68 charged with a burning-supporting gas such as oxygen through a burning-supporting gas pipe 74 and a manual valve 73.
Next, the use of this flux supply device is described.
When using the automatic brazing apparatus 76, the manual valves 70 and 72 are opened to supply the mixed gas composed of the gas flux produced through vaporization (gasification) of the liquid flux 15 in the flux storage tank 11 and the combustible gas from the combustible gas cylinder 67 to the automatic brazing apparatus 76 through the mixed gas pipe 20. The manual valve 73 is also opened to supply the burning-supporting gas in the burning-supporting gas cylinder 68 to the automatic brazing apparatus 76 through the burning-supporting gas pipe 74.
The combustible gas supplied from the combustible gas cylinder 67 is discharged into the liquid flux 15 in the flux storage tank 11 from the lower end of the gas blow-in pipe 18. This discharge causes part of the liquid flux 15 to vaporize to produce the gas flux, which forms the mixed gas in the flux storage tank 11 together with the combustible gas supplied from the gas blow-in pipe 18.
This mixed gas is sent out from the flux storage tank 11 through the outlet 21 and supplied to the automatic brazing apparatus 76 through the mixed gas pipe 20. When the automatic brazing apparatus 76 is in operation, the liquid flux 15 stored in the flux storage tank 11 vaporizes and thus gradually diminishes. Hence, in order to fill up the reduction of the liquid flux 15, the first and second manual valves 31 and 35 of the liquid flux replenishing device are kept open.
Accordingly, as the liquid flux 15 in the flux storage tank 11 diminishes and its surface level S1 lowers, the liquid flux 15 contained in the replenishing tank 25 is soon supplied into the flux storage tank 11 through the liquid flux supply pipe 17. Thus, as long as the liquid flux 15 is contained in the liquid flux replenishing device, the surface level S1 of the liquid flux 15 in the flux storage tank 11 is always kept unchanged, so that the mixed gas can be continuously supplied to the automatic brazing apparatus 76.
When the liquid flux 15 contained in the liquid flux replenishing device runs low, the replenishing tank 25 must be replaced by a new one. For the replacement, first, the first manual valve 31 and the second manual valve 35 are both closed. Next, the cam lock coupling 32 is operated to separate the second pipe 42 and the components attached on it from the cam lock coupling 32. In this condition, the first manual valve 31 is closed, so that the liquid flux, possibly remaining in the first pipe 41 etc., will not leak out.
Then the opening 26 of the replenishing tank 25 is removed from the first pipe 41 and a new replenishing tank 25 filled with the liquid flux 15 is connected to the first pipe 41. The cam lock coupling 32 is then operated to connect the second pipe 42 to the cam lock coupling 32, and then the first manual valve 31 and the second manual valve 35 are both opened. The liquid flux 15 in the new replenishing tank 25 is thus supplied into the flux storage tank 11 through the liquid flux supply pipe 17, so that the mixed gas can always be supplied continuously to the automatic brazing apparatus 76 from the flux storage tank 11.
The above-described conventional flux supply device encounters no particular problem during ordinary operation of the automatic brazing apparatus 76. However, a problem arises when the brazing work with the automatic brazing apparatus 76 is stopped at the end of the working hours or when the automatic brazing apparatus 76 is started on the next day, for example.
For example, when the brazing work is finished at the end of the working hours, the operation of the automatic brazing apparatus 76 is stopped and the manual valves 70, 72 and 73 are closed. On the next day, when the manual valves 70, 72 and 73 are opened to use the automatic brazing apparatus 76, the surface level S1 of the liquid flux 15 in the flux storage tank 11 may considerably vary.
Now the pressure equilibrium condition between the liquid flux 15 in the flux storage tank 11 and the liquid flux 15 in the replenishing tank 25 is described first. When the pressure in the space above the liquid flux 15 in the flux storage tank 11 is taken as P1 (normally 1 Kg/cm2 or lower), the pressure in the space above the liquid flux 15 in the replenishing tank 25 as P2, the vertical distance between the surface level S1 of the liquid flux 15 in the flux storage tank 11 and the surface level S2 of the liquid flux 15 in the replenishing tank 25 as H, the density of the liquid flux 15 as xcfx81, and the acceleration of gravity as xcfx81, then
P1=Hxcfx81g+P2 
The condition at the beginning of the operation as described on the above is now considered on the basis of this equation. First, when the manual valve 70 is opened at the beginning of operation, the pressure P1 in the flux storage tank 11 rises as the combustible gas is discharged through the gas blow-in pipe 18. This forces the vertical distance H to increase in the equation above, and as a result the liquid flux 15 in the flux storage tank 11 will go up in the liquid flux supply pipe 17 to raise the surface level S2 of the liquid flux 15 in the replenishing tank 25. While the liquid flux supply pipe 17 is usually filled with new liquid flux 15 supplied from the replenishing tank 25, the old liquid flux 15 stored in the flux storage tank 11 mixes in it.
Next, the manual valve 72 is opened in this condition. When the manual valve 72 is opened, the mixed gas produced in the flux storage tank 11 is rapidly supplied to the automatic brazing apparatus 76 through the mixed gas pipe 20. This decreases the pressure P1 in the flux storage tank 11. Then the distance H will decrease in the equation above. That is to say, in this condition, the surface level S2 of the liquid flux 15 in the replenishing tank 25 lowers, which forces part of the liquid flux 15 into the flux storage tank 11 through the liquid flux supply pipe 17. Then the surface level S1 of the liquid flux 15 in the flux storage tank 11 goes up. The pressure P2 in the replenishing tank 25 may become negative and then the replenishing tank 25 may be dented.
When the surface level S1 in the flux storage tank 11 varies as explained above, the distance between the surface level S1 and the lower end of the gas blow-in pipe 18 through which the combustible gas is discharged varies, which varies the amount of discharged combustible gas. It is then difficult to supply the automatic brazing apparatus 76 with the mixed gas at stable concentration.
Furthermore, since the replenishing tank 25 is closed to the outside, the pressure P2 in the space in it becomes negative when the liquid flux 15 moves downward. This may dent the body of the replenishing tank 25, and then the pressure P2 varies to cause the distance H to vary in the equation shown above. As a result, the surface level S1 in the flux storage tank 11 will vary, too.
The variation of the surface level is caused not only at the end or beginning of the operation, but the pressure P1 in the flux storage tank 11 is varied also by variation of the flow rate of the mixed gas or variation of the atmospheric temperature etc. during the operation of the automatic brazing apparatus 76, and as a result the surface level S1 will vary. It is therefore difficult for the conventional flux supply device to constantly supply the mixed gas at stable pressure and stable concentration, leading to deterioration of the brazing quality of the brazing apparatus.
An object of the present invention is to stably supply a liquid flux into a flux storage tank even when the pressure in the flux storage tank is varied.
Another object of the present invention is to provide a flux supply device and a liquid flux supply method which suppress the variation of the surface level in the flux storage tank.
To achieve the objects above, a first aspect of the present invention is directed to a flux supply device for supplying a mixed gas composed of a gas flux and a combustible gas to a brazing apparatus, where the flux supply device comprises: a flux storage tank for storing a liquid flux; a gas blow-in pipe for blowing the combustible gas into the liquid flux stored in the flux storage tank; a liquid flux supply pipe for supplying the liquid flux into the flux storage tank, the liquid flux supply pipe having its lower end located above the lower end of the gas blow-in pipe; a liquid replenishing portion for holding the liquid flux, the liquid replenishing portion being located above the liquid flux supply pipe and having its lower end opened; a first automatically opened/closed valve connected to the lower end of the liquid replenishing portion; a second automatically opened/closed valve connected to the upper end of the liquid flux supply pipe; a liquid holding portion for holding the liquid flux, the liquid holding portion being connected between the lower end of the first automatically opened/closed valve and the upper end of the second automatically opened/closed valve; and a control portion for controlling the first automatically opened/closed valve and the second automatically opened/closed valve so that one automatically opens and closes and then the other automatically opens and closes, alternately and repeatedly.
With this structure, at least one of both ends of the liquid holding portion is always closed by the first automatically opened/closed valve or the second automatically opened/closed valve.
According to a flux supply device of a second aspect of the present invention, in the structure of the first aspect, the control portion provides control so that the amount of the liquid flux that can be supplied from the liquid holding portion into the liquid flux supply pipe while the first automatically opened/closed valve and the second automatically opened/closed valve are opened and closed in a given time period is larger than the amount of the liquid flux consumed while the mixed gas is sent out from the flux storage tank in the given time period.
With this structure, the liquid flux is always contained in the liquid flux supply pipe.
According to a flux supply device of a third aspect of the invention, in the structure of the second aspect, the control portion can change the timing for opening and closing the first automatically opened/closed valve and the second automatically opened/closed valve.
With this structure, the amount of liquid flux supplied into the flux storage tank can be easily adjusted in accordance with the variation of the amount of mixed gas that the flux supply device supplies.
According to a flux supply device of a fourth aspect of the invention, in the structure of any of the first to third aspects, the control portion provides control so that a given time passes from when one of the first automatically opened/closed valve and the second automatically opened/closed valve is closed to when the other is opened.
With this structure, both ends of the liquid holding portion are completely closed for the given time period.
A fifth aspect of the invention is directed to a flux supply device for supplying a mixed gas composed of a gas flux and a combustible gas to a brazing apparatus, where the flux supply device comprises: a flux storage tank for storing a liquid flux; a gas blow-in pipe for blowing the combustible gas into the liquid flux stored in the flux storage tank; a liquid flux supply pipe for supplying the liquid flux into the flux storage tank, the liquid flux supply pipe having its lower end located above the lower end of the gas blow-in pipe; a liquid replenishing portion for holding the liquid flux, the liquid replenishing portion being located above the liquid flux supply pipe and having its lower end opened; a rotary valve connected between the upper end of the liquid flux supply pipe and the lower end of the liquid replenishing portion; and a control portion for providing control to rotate the rotary valve so that an open hole formed in the body of the rotary valve alternately communicates with the liquid flux supply pipe and the liquid replenishing portion.
With this structure, the liquid replenishing portion and the liquid flux supply pipe are not allowed to directly communicate with each other.
According to a flux supply device of a sixth aspect of the invention, in the structure of the fifth aspect, the control portion provides control so that the amount of the liquid flux that can be supplied from the open hole into the liquid flux supply pipe while the rotary valve rotates in a given time period is larger than the amount of the liquid flux consumed while the mixed gas is sent out from the flux storage tank in the given time period.
With this structure, the liquid flux is always contained in the liquid flux supply pipe.
A seventh aspect of the present invention is directed to a liquid flux supply method for use with a flux supply device for supplying a mixed gas of a gas flux and a combustible gas to a brazing apparatus, wherein a liquid flux held in a liquid replenishing portion located above a storage tank storing the liquid flux is supplied into the storage tank through a liquid holding portion which is controlled so that its one end automatically opens and closes and then the other end automatically opens and closes, alternately and repeatedly.
With this structure, the variation of pressure in the storage tank does not affect the liquid replenishing portion.
As stated above, according to the flux supply device of the first aspect, at least one of both ends of the liquid holding portion is always closed, so that the liquid replenishing portion is not affected even if the pressure in the flux storage tank varies, and the liquid flux can be stably supplied into the flux storage tank. This suppresses the variation of the surface level of the liquid flux stored in the flux storage tank.
According to the flux supply device of the second aspect, in addition to the effect of the first aspect, the liquid flux is always contained in the liquid flux supply pipe and the surface level of the liquid flux stored in the flux storage tank can be kept unchanged even when the amount of the used mixed gas varies. Therefore the mixed gas can always be stably supplied to the brazing apparatus to enhance the reliability of the apparatus.
According to the flux supply device of the third aspect, in addition to the effect of the second aspect, the amount of liquid flux supplied into the flux storage tank can be easily adjusted in accordance with the amount of consumed mixed gas, thus providing greater convenience.
According to the flux supply device of the fourth aspect, in addition to the effect of any of the first to third aspects, both ends of the liquid holding portion are completely closed for a given time period, which completely prevents the pressure variation in the tank from affecting the liquid replenishing portion, thus providing improved reliability.
According to the flux supply device of the fifth aspect, the liquid replenishing portion and the liquid flux supply pipe do not directly communicate with each other, so that the liquid flux can be stably supplied into the flux storage tank even if the pressure in the flux storage tank or the liquid replenishing portion varies. This suppresses the variation of the surface level of the liquid flux stored in the flux storage tank.
According to the flux supply device of the sixth aspect, in addition to the effect of the fifth aspect, the liquid flux is always contained in the liquid flux supply pipe, and the surface level of the liquid flux stored in the flux storage tank can be kept unchanged even when the amount of used mixed gas varies. Therefore the mixed gas can always be stably supplied to the brazing apparatus to improve the reliability.
According to the flux supply method of the seventh aspect, the variation of pressure in the storage tank does not affect the liquid replenishing portion, so that the liquid flux can be stably supplied. This suppresses the variation of the surface level of the liquid flux stored in the flux storage tank.
These and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.